Etching method with less waste gases

ABSTRACT

An etching method with less waste gases. Firstly, provide a substrate covered by a dielectric layer, and put both the substrate and the dielectric layer into a chamber that is coupled with a power source and a C 3 F 8  reactive gases source. Next, provide a plasma inside the chamber under an environment with a low RF power, and a low pressure. Finally, terminate the existence of the plasma and move both the substrate and the etched dielectric later out the chamber.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an etching method with lesswaste gases. More particularly, this invnetion relates to a method forreducing the quantity of the by-product(s) of an etching process byusing the C3F8 with some specific values of some etching parameters.

[0003] 2. Description of the Prior Art

[0004] Conventional semiconductor fabrication technologies usually etchthe dielectric layer, such as the silicon dioxide layer and the siliconnitride layer, by some etchants such as CF₄ or C₂F₆. However, theseconventional etchants have a significant disadvantage: the quantity ofwaste gases is irnegligible, even is huge. Hence, the production cost isincreased for many inputted raw materials are wasted, and the earthenvironment is strongly damaged by these expelled waste gases. Herein,FIG. 1A shows some datas to briefly describe the relations between thequantity of waste gases and some practical values of some etchingparameters, the unit of waste gases is MMTCE (million metric tun carbonequivalent).

[0005] To improve this disadvantage, some newly developed semiconductorfabrication technologies use some new etchant(s) to etch the dielectriclayer. For example, the 3M company presented a method that uses the C₃F₈to etch the dielectric layer with the following parameters' values: RFpower is about 1200 W (Walt) to 1800 W, flow rate of C₃F₈ is larger than150 sccm, and pressure is larger than 3 torr. Herein, according to thedatas that the 3M company makes public, FIG. 1B shows the relationsbetween the quantity of waste gases and some practical values of someetching parameters.

[0006] Clearly, according to 3M company's datas, the application of C3F8could effectively reduce the quantity of waste gases, even the quantityof waste gases could be further reduced, and even both the consumedmaterial and consumed power could be further reduced.

SUMMARY OF THE INVENTION

[0007] One main object of the present invention is to reduce thequantity of waste gases which are formed while the dielectric layerbeing treated.

[0008] Another main object of the present invention is to improve theexistent etch technologies without strongly amending the details of theexistent etch technologies.

[0009] To achieve these objects, the present invention amends the valuesof some parameters of the etching process which uses the C3F8 as theetchant. The present invention reduces the flow rate of input C3F8,reduces the pressure inside the chamber, and reduces the power of usedRF power source. Thus, the present invnetion reduces the probabilitythat the plasma incompletely react with the dielectric layer, thepresent invention also reduces the ratio that some raw materials are notused, and then the quantity of waste gases which induced by theincomplete reaction and non-reacted materials are effectively reduce.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] A more complete appreciation and many of the attendant advantagesthereof will be readily obtained as the same becomes better understoodby reference to the following detailed description when considered inconnection with the accompanying drawings.

[0011]FIG. 1A shows the relations between some etching parameters andthe quantity of waste gases in accordance with the conventionaltechnologies;

[0012]FIG. 1B shows the relations between some etching parameters andthe quantity of waste gases in accordance with the 3M company's methodthat uses the C3F8 as the etchant;

[0013]FIG. 2A through FIG. 2H shows the essential flow of one preferredembodiment of this invention;

[0014]FIG. 3A through FIG. 3C shows the relations between some etchingparameters and the quantity of waste gases while using the presentinvention to etch SiN, SiON and PEOX;

[0015]FIG. 4 shows some suggested values of some parameters which couldbe used to etch SiN, SiON, and PEOX;

[0016]FIG. 5A through FIG. 5I show two essential flowchart of anotherpreferred embodiment of this invention; and

[0017]FIG. 6 shows the essential flowchart of the other preferredembodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] One preferred embodiment of this present invention is an etchingmethod with less waste gases, at least has following essential steps insequence:

[0019] As FIG. 2A shows, provides substrate 10 that is covered bydielectric layer 11 and pattern mask 12 in sequence. Herein, thematerial of dielectric layer 11 usually is chosen from a groupconsisting of SiO₂, SiN and SiO_(X)N_(y), where both X and Y beingpositive integers.

[0020] As FIG. 2B shows, puts substrate 10 with both dielectric layer 11and pattern mask 12 on the wafer holder 14 inside chamber 13, Wherein,chamber 13 is coupled with reactive gases source 15 and RF power source16. Moreover, reactive gases source 15 is used to input numerous C₃F₈molecules through both first pipeline 17 and injector 18 into chamber13, and RF power source 16 is used to input a RF power through secondpipeline 18 into chamber 13.

[0021] As FIG. 2C shows, forms plasma 195 inside chamber 13 under theenvironment of a low C₃F₈ flow rate, a low RF power, and a low pressure,and let plasma 195 react with and etch partial dielectric layer 11 thatis not covered by pattern mask 12. Herein, the pressure of the lowpressure environment usually is smaller than about 3 torrs, the low RFpower usually is about from 900 W to 1300 W, and the low C₃F₈ flow rateusually is smaller than about 150 sccm. In addition, it is possible toinput the N₂O into chamber 13, but the flow rate of the N₂O gas is notthe key point of the present embodiment.

[0022] Further, in the embodiment, plasma 195 could comprise one of thefollowing components: N or Ar, plasma also could comprise one of thefollowing components: N₂O, O, and NO₂.

[0023] As FIG. 2D shows, terminate the existence of plasma 195 and movesubstrate 10, residual dielectric layer 11, and pattern mask 12 outchamber 13.

[0024] Indisputably, because that the byproducts, such as waste gases,are formed by the reaction between plasma 195 and dielectric layer 11,the application of the embodiment is not limited by FIGS. 2A-2D thatetches partial dielectric layer 11 to form an opening inside dielectriclayer 11, the application of the embodiment should be limited byapplying plasma 195, which formed by the present conditions, to treatdielectric layer 11.

[0025] For example, the embodiment could be used to completely thindielectric layer 11, as shown in FIG. 2E to FIG. 2H. In the mean time,pattern mask is omitted, dielectric layer 11 being completely etch byplasma 195 after dielectric layer 11 is formed, and then the thicknessof dielectric layer 11 is overall thinned.

[0026] In order to describe the relation between the adjustedparameters' values and the quantity of waste gases in the presentembodiment, FIG. 3A through FIG. 3C separately shows three practicalapplications of this embodiment. Herein, these figures show the flowrate of C₃F₈, the flow rate of N₃O, the pressure inside the chamber, thepower of the RF power source, the quantity of waste gases (in the unitof MMTCE), and the MMTEC reduction percentage while comparing with theFIG. 1A. FIG. 3A shows the case of etching SiN, FIG. 3B shows the caseof etching SiON, and FIG. 3C shows the case of etching PEOX, the oxideformed by the plasma enhanced chemical vapor deposition.

[0027] By comparing FIG. 3A through FIG. 3B with FIG. 1A through FIG.1B, indisputably, the quantity of waste gases of this present embodimentnot only is strongly lesser than the conventional technologies whichnever use the C₃F₈ as the etchant, but also is lesser significantly thanthe 3M method which also uses the C₃F₈ as the etchant. Moreover, bycomparing the required parameters' values of this embodiment and therequired parameters' values of the 3M company's method, indisputably,the present embodiment required lesser C₃F₈ gas, lesser RF power, andlower pressure. Hence, the present embodiment not only reduces thequantity of waste gases, but also reduces the consumption of rawmaterials. Further, even the present embodiment required lesser pressurethan the 3M company's method, owing to the order of pressure used by themethod also is torr, the required pressure could be easily provided bythe conventional technology, and then no specific difficulty or extracost would be appeared.

[0028] Finally, to balance some requirements such as reducing wastegases and reducing cost, the present embodiment provides some suggestedparameters' values, separately corresponds to SiN, SiON, and PEOX.However, it should be emphasized that these suggested parameters' valuesonly are a specific suggestion, the main characteristics and availableparameters' values are not limited by FIG. 4. In short, the presentembodiment uses C₃F₈ to etch the dielectric layer by the application ofRF power is about 900 W to 1300 W, pressure is lesser than 3 torrs, andflow rate of C₃F₈ is lesser than about 150 sccm.

[0029] Another preferred embodiment of this invention also is an etchingmethod with less waste gases. Details of the embodiment are basicallysimilar with the previous embodiment, both embodiments being focused onhow to form the required plasma for treating dielectric layer but notbeing focused on the dielectric layer is treated by the formed plasma.The main differences between this current embodiment and the leastembodiment is that the current embodiment only requires low RF power andlow pressure but does not limit the flow rate of C3F8.

[0030] The current embodiment is based on the following experimentalresults: the flow rate of C3F8 essentially only affect how manyparticles, such as ions, could be used to etch. In fact, whether areaction is complete, how fast the reacting rate is, and how many rawmaterials are wasted are essentially decided by the pressure inside thechamber and the RF power inputted into the chamber.

[0031] Clearly, to compare with the 3M company's method, the presentinvention also uses the C₃F₈ as the etchant, but the present inventionuses both lower pressure and lower RF power, even uses lower C₃F₈ flowrate, than the 3M company's method. However, the differences aresignificant and non-obvious.

[0032] For most of the conventional etch technologies, include the 3Mcompany's method, the key issues are increasing both the etch rate andthe etch selectivity, and the adjustment of all related parameters isfocused on how to achieve previous issues. In this way, the routine testof all related parameters' values would not try to reduce the wastegases.

[0033] Next, most of the conventional etch technologies, include the 3Mcompany's method, only disclose and/or hint something about how toincrease the etch rate and/or the etch selectivity. For example, the 3Mcompany's method only disclosed a preferred range of these parameters,but never discloses/teaches what is the benefit to reduce the values ofthese parameters, even never clearly discloses/teaches anything aboutreducing the values of these parameters.

[0034] Accordingly, it is not reasonable to consider that 3M company'smethod had disclosed/taught the etching process by using C₃F₈ could bepreformed with the parameter's value that presented by these previouspresent embodiments.

[0035] Accordingly, the invention forms a plasma under an environmentwith low pressure and low RF power, even with low C₃F₈ flow rate, anduses the plasma to treat a dielectric layer to reduce the quantity ofwaste gas. Significantly, the invention not only could treat anydielectric layer located on the substrate, or called as wafer, but alsocould treat any dielectric layer which could react with the plasma.

[0036] For example, wafer holder 14 shown in FIGS. 2A-2H only is asimplified example. To effectively fixed the wafer (substrate 10), thereal wafer holder 145 usually is not completely covered by the wafer,and the edge of the wafer is partially surrounded, even hold, by thewafer holder 145. Herein, FIG. 5A shows a possible real wafer holderl4.On the other wafer, the practical formation of a dielectric layerusually is not perfectly precise to let the dielectric layer only beformed on a wafer, and then the dielectric layer usually is diffused toother places. Therefore, as FIG. 5B shows, except the fabricationparameters are perfect to let all dielectric layer 11 is thoroughlyremoved by plasma 195, after the semiconductor fabrication is finishedand the wafer is moved, partial dielectric layer 11 is left on the waferholder 14, especial on the part not covered by the wafer during thefabrication, and on the sidewall of chamber 13. Clearly, the non-removeddielectric layer 11 would be a pollution source in the sequentialfabrication inside chamberl3.

[0037] Therefore, another preferred embodiment of this invention is amethod of cleaning the chamber with less waste gases. The embodiment atleast has following essential steps:

[0038] As shown in FIG. 5B, provide chamber 13 to be cleaned. Chamber 13is coupled with power source 15 and C₃F₈ reactive gases source 16.Dielectric layer 11 is located on the sidewall of chamber 13 and waferholder 145.

[0039] As shown in Fig, 5C, form plasma 195 inside chamber 13 under anenvironment having a low RF power and a low pressure, and treatdielectric layer 11 by plasma 195. Moreover, it is allowable to lowerthe flow rate of C₃F₈ during the formation of plasma 195, an also ispossible to low the C₃F₈ flow rate of during the existence of plasma195.

[0040] As shown in FIG. 5D, terminate the existence of plasma 195.Surely, it is better to terminate after no dielectric layer 11 is leftinside chamber 13.

[0041] Certainly, because the semiconductor fabrication is changeable,the embodiment has other variations. For example, as shown in FIG. 5E,it is possible that the surface of wafer holder 14ahs been covered bydielectric layer 115 before wafer 10 is putted.

[0042] Obviously, as shown in FIG. 5F and FIG. 5G, wafer 10 is locatedon dielectric layer 115 during a fabricating process that formsdielectric layer 11 on dielectric layer. Herein, dielectric layer 115 isindependent of dielectric layer 11, material of dielectric layer 115could be different from the material of dielectric layer 11.

[0043] Again, after wafer 10 being removed, as shown in FIG. 5H, plasma195 is formed under a environment with the low PR frequency and the lowpressure and is used to remove both dielectric layer 11 and dielectriclayer 115. Surely, it is possible to reduce the C₃F₈ flow rate of duringthe existence of plasma 195.

[0044] Clearly, as shown in FIG. 5I, while the reaction with plasma 195being enough, all dielectric layer 11 and dielectric layer 11 on waferholder 105 would be cleaned and removed by plasma 195.

[0045] Furthermore, because that the experimental results how that thequantity of waste gases is strongly dependent on the density of the CF2*radials, another preferred embodiment of this invention still being anetching method with less waste gases. As FIG. 6 shows, at least hasfollowing essential steps:

[0046] As preparation block 21 shows, form a dielectric layer on asubstrate. Surely, the dielectric layer usually is covered by apatterned mask to define which part of the dielectric layer should beetched.

[0047] As etch block 22 shows, applies a plasma to the dielectric layerso let at least partial the dielectric layer be etched by the plasmaunder a low RF power and low pressure environment. Herein, the mainmaterial of the plasma is the fluorocarbon which could produce numerousCF2* radials under the low RF power and low pressure environment.Herein, the standard of numerous CF2* radials means that thefluorocarbon could produce more CF2* radials than CF4, and also couldproduce more CF2* radials than C2F6.

[0048] Indisputably, the main characteristic of this preferredembodiment is that the usage of fluorocarbon (molecules) which couldproduce numerous CF2* radials.

[0049] Consider that each the carbon atom has four outer shell electronsand each fluorine atom has one outer electron, consider that the strainchain usually only use the single bond to connect neighboring atoms, andconsider that the lighter molecules are easier to product/control/reactthan the heavier molecules. It is reasonable that straight chainfluorocarbon molecules could provide the most fluorine ions than otherfluorocarbon molecules, and then the etch result of straight chainfluorocarbon molecules would be better than other fluorocarbonmolecules.

[0050] Therefore, by the usage of straight chain fluorocarbon molecules,the preferred embodiment could effectively improve the efficiency of thedielectric layer etching process.

[0051] Besides, because the main difference between this preferredembodiment and last preferred embodiments is that C₃F₈ is replaced bythe fluorocarbon which produce more CF2* radials, many details of thepreferred embodiment are similar with that of the previous preferredembodiments. For example, by the usage of both lower pressure and lowerRF power, even lower fluorocarbon flow rate, during the existence of theplasma, the quantity of the waste gases could be further effectivereduced.

[0052] Obviously, numerous additional modifications and variations ofthe present invention are possible in light of the above teachings. Itis therefore to be understood that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed herein.

What is claimed is:
 1. A method of etching with less waste gases,comprising: providing a substrate, said substrate being covered by adielectric layer; putting said substrate inside a chamber, said chamberbeing coupled with a power source and a C₃F₈ reactive gases source;forming a plasma inside said chamber under an environment having a lowRF power and a low pressure; etching said dielectric layer by saidplasma, and terminating the existence of said plasma and moving saidsubstrate out said chamber.
 2. The method of claim 1, further comprisingthe step of forming said plasma under an amended environment having alow C₃F₈ flow rate, a low RF power and a low pressure.
 3. The method ofclaim 1, further comprising the step of covering a pattern mask on saiddielectric layer before said dielectric layer being etched by saidplasma, whereby said plasma only etch partial said dielectric layerwhich is not covered by said pattern mask.
 4. The method of claim 3,further comprising the step of etching said pattern mask by said plasma.5. The method of claim 2, further comprising the step of covering apattern mask on said dielectric layer before said dielectric layer beingetched by said plasma, whereby said plasma only etch partial saiddielectric layer which is not covered by said pattern mask.
 6. Themethod of claim 5, further comprising the step of etching said patternmask by said plasma.
 7. The method of claim 1, wherein the material ofsaid dielectric layer is chosen from a group consisting of SiO₂, SiN andSiO_(x)N_(y), both X and Y being positive integers.
 8. The method ofclaim 1, said low RF power being about from 900 W to 1300 W.
 9. Themethod of claim 1, the pressure of said environment being smaller thanabout 3 torrs.
 10. The method of claim 2, said low C₃F₈ flow rate beingsmaller than about 150 sccm.
 11. The method of claim 1, said plasmafurther comprising one of the following elements: He, Ar, N₂O, O, andNO₂,
 12. A method of etching with less waste gases, comprising: forminga dielectric layer on a substrate; and applying a plasma on saiddielectric layer to let at least partial said dielectric layer be etchedby said plasma under an environment having a low RF power and a lowpressure, wherein the main material of said plasma is the fluorocarbonwhich could produce a plurality of CF2* radials under said environmentwhich has low RF power and low pressure environment.
 13. The method ofclaim 12, said fluorocarbon producing more CF2* radials than CF4 undersaid environment, said fluorocarbon also producing more CF2* radialsthan C2F6 under said environment.
 14. The method of claim 12, furthercomprising the step of lowering the flow rate of said fluorocarbonduring both the formation of said plasma and the existence of saidplasma.
 15. The method of claim 12, said low RF power being about from900 W to 1300 W.
 16. The method of claim 12, the pressure of saidenvironment being smaller than about 3 torrs.
 17. The method of claim14, said low C₃F₈ flow rate being smaller than about 150 sccm.
 18. Amethod of cleaning the chamber with less waste gases, comprising:providing a chamber to be cleaned, said chamber being coupled with apower source and a C₃F₈ reactive gases source, a dielectric layer beinglocated on the sidewall of said chamber and on a wafer holder; forming aplasma inside said chamber under an environment having a low RF powerand a low pressure; treating said dielectric layer by said plasma; andterminating the existence of said plasma.
 19. The method of claim 18,further comprising the step of lowering the flow rate of said C₃F₈during both the formation of said plasma and the existence of saidplasma.
 20. The method of claim 18, said dielectric layer being locatedon a partial surface of said wafer holder, wherein said partial surfaceis not covered by a wafer while said wafer being treated by saidchamber.